论文标题
多余的宇宙学含义
Cosmological implications of the KOTO excess
论文作者
论文摘要
Koto实验报告了超过标准模型预测的$ k_l \toπ^0ν\barν$事件的过量，与Grossman-Nir（GN）结合在一起。 GN结合在此渠道中严重限制了对多余的新物理解释，但另一种可能性是，观察到的事件完全源于另一个过程：$ k_l \toπ^0x $的衰减，其中$ x $表示一个或多个新的不可见物种。我们介绍了一类模型来研究这种情况，其中有两个轻标量扮演$ x $的角色，我们研究了两个新状态的较轻的可能性也可能解释了宇宙学的暗物质（DM）。我们表明，除了涉及多余的相互作用之外，还可以在存在其他相互作用的情况下热产生该物种。相反，在模型的最小版本中，必须非热生产DM。在这种情况下，避免过度生产对低能理论的结构施加限制。此外，这一要求对早期宇宙的再加热规模产生了重大影响，通常更喜欢低但观察允许的O（10 MeV）的温度。我们讨论了天体物理和陆地签名，这些签名将在未来几年内进一步测试该范式。
The KOTO experiment has reported an excess of $K_L\toπ^0ν\barν$ events above the Standard Model prediction, in tension with the Grossman-Nir (GN) bound. The GN bound heavily constrains new physics interpretations of an excess in this channel, but another possibility is that the observed events originate from a different process entirely: a decay of the form $K_L\toπ^0X$, where $X$ denotes one or more new invisible species. We introduce a class of models to study this scenario with two light scalars playing the role of $X$, and we examine the possibility that the lighter of the two new states may also account for cosmological dark matter (DM). We show that this species can be produced thermally in the presence of additional interactions apart from those needed to account for the KOTO excess. Conversely, in the minimal version of the model, DM must be produced nonthermally. In this case, avoiding overproduction imposes constraints on the structure of the low-energy theory. Moreover, this requirement carries significant implications for the scale of reheating in the early Universe, generically preferring a low but observationally permitted reheating temperature of O(10 MeV). We discuss astrophysical and terrestrial signatures that will allow further tests of this paradigm in the coming years.
